Online Ruler
Measure on-screen in cm, mm, inches or px — DPI-calibrated.
See how it works
Watch a quick simulation of this tool in action — no file needed.
How to use Online Ruler
Follow these steps — everything happens instantly in your browser.
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Step 1. Pick a unit — cm, mm, inch or pixel.
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Step 2. Calibrate DPI to match your physical screen.
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Step 3. Move your cursor over the stage to measure.
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Step 4. Read x/y measurements in real time.
Why use this tool
Private by design
All processing happens locally in your browser. Open DevTools → Network and you'll see zero file uploads. Ever.
Instant
No upload wait, no queue, no server round-trip. Results appear the moment you drop a file.
Free & unlimited
No accounts, no watermarks, no daily caps. Use it as many times as you like, forever.
Works everywhere
Desktop, tablet or phone — every tool is responsive and installable as a PWA for offline use.
Frequently asked questions
Everything you might want to know about online ruler.
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